NUMERICAL ANALYSIS ON STRESS INDUCED CORROSION WITH EMPHASIS ON TI-ALLOY TOTAL HIP ARTHROPLASTY STEM FAILURE

摘要

Modular designs give orthopaedic surgeons a greater flexibility to custom fit the implant to the patients bone while performing total hip arthroplasty. Titanium alloy (Ti6Al4V (ASTM F-136)) is typically used for modular hip implant stems. This highly corrosion resistant alloy forms passive surface oxide films spontaneously. However, with modular designs, micro-motion may occur at the taper junctions during mechanical loading. Crevices between the taper junctions may allow the body fluids to enter and remain stagnant. These conditions make the modular tapers susceptible to fatigue and mechanically assisted crevice corrosion. The in vivo degradation of metal alloy implants compromises the structural integrity. The influence of stress induced corrosion and pitting leading to the in vivo catastrophic failure of a titanium-alloy modular implant in cementless total hip arthroplasty was numerically investigated. The effect of pit geometric parameters are discussed in terms of taper performance.